Support first letter navigation in Panel.

chrome/browser/resources/chromeos/chromevox/cvox2/background/panel_menu.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview A drop-down menu in the ChromeVox panel.
  */
 
 goog.provide('PanelMenu');
 goog.provide('PanelNodeMenu');
@@ skipping 44 matching lines @@
     * @private
     */
   this.updateScrollbarsTimeout_ = null;
 
   /**
    * The current active menu item index, or -1 if none.
    * @type {number}
    * @private
    */
   this.activeIndex_ = -1;
+
+  this.menuElement.addEventListener(
+      'keypress', this.onKeyPress_.bind(this), true);
 };
 
 PanelMenu.prototype = {
   /**
    * @param {string} menuItemTitle The title of the menu item.
    * @param {string} menuItemShortcut The keystrokes to select this item.
    * @param {Function} callback The function to call if this item is selected.
    * @return {!PanelMenuItem} The menu item just created.
    */
   addMenuItem: function(menuItemTitle, menuItemShortcut, callback) {
@@ skipping 105 matching lines @@
    * Get the callback for a menu item given its DOM element.
    * @param {Element} element The DOM element.
    * @return {Function} The callback.
    */
   getCallbackForElement: function(element) {
     for (var i = 0; i < this.items_.length; i++) {
       if (element == this.items_[i].element)
         return this.items_[i].callback;
     }
     return null;
+  },
+
+  /**
+   * Handles key presses for first letter accelerators.
+   */
+  onKeyPress_: function(evt) {
+    var query = String.fromCharCode(evt.charCode).toLowerCase();
+
+    for (var i = this.activeIndex_ + 1; i < this.items_.length; i++) {
+      if (this.items_[i].text.toLowerCase().indexOf(query) == 0) {
+        this.activateItem(i);
+        break;
+      }
+    }
   }
 };
 
 /**
  * @param {string} menuMsg The msg id of the menu.
  * @param {chrome.automation.AutomationNode} node ChromeVox's current position.
  * @param {AutomationPredicate.Unary} pred Filter to use on the document.
  * @extends {PanelMenu}
  * @constructor
  */
@@ skipping 32 matching lines @@
 PanelNodeMenu.prototype = {
   __proto__: PanelMenu.prototype,
 
   /** @override */
   activate: function() {
     var activeItem = this.activeIndex_;
     PanelMenu.prototype.activate.call(this);
     this.activateItem(activeItem);
   }
 };